dt-bindings: mdio: Clarify binding document

The described GPIO reset property is applicable to *all* child PHYs. If
we have one reset line per PHY present on the MDIO bus, these
automatically become properties of the child PHY nodes.

Finally, indicate how the RESET pulse width must be defined, which is
the maximum value of all individual PHYs RESET pulse widths determined
by reading their datasheets.

Fixes: 69226896ad ("mdio_bus: Issue GPIO RESET to PHYs.")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/mdio.txt

@@ -3,13 +3,17 @@ Common MDIO bus properties.
 These are generic properties that can apply to any MDIO bus.
 
 Optional properties:
-- reset-gpios: List of one or more GPIOs that control the RESET lines
-  of the PHYs on that MDIO bus.
-- reset-delay-us: RESET pulse width in microseconds as per PHY datasheet.
+- reset-gpios: One GPIO that control the RESET lines of all PHYs on that MDIO
+  bus.
+- reset-delay-us: RESET pulse width in microseconds.
 
 A list of child nodes, one per device on the bus is expected. These
 should follow the generic phy.txt, or a device specific binding document.
 
+The 'reset-delay-us' indicates the RESET signal pulse width in microseconds and
+applies to all PHY devices. It must therefore be appropriately determined based
+on all PHY requirements (maximum value of all per-PHY RESET pulse widths).
+
 Example :
 This example shows these optional properties, plus other properties
 required for the TI Davinci MDIO driver.
@@ -21,7 +25,7 @@ required for the TI Davinci MDIO driver.
 		#size-cells = <0>;
 
 		reset-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
-		reset-delay-us = <2>;   /* PHY datasheet states 1us min */
+		reset-delay-us = <2>;
 
 		ethphy0: ethernet-phy@1 {
 			reg = <1>;